1. Field of the Invention
The present invention relates to local area networks (LANs). More specifically, the present invention relates to interfacing units for use with local area networks.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
Local area networks (LANs) facilitate data communication between computing systems (such as a network of data terminal equipments, network workstations, personal computers, and the like, individually referred to hereinafter as a "host"). Currently, several types of LAN systems are used widely in the art. Most systems may be classified generally as either an Ethernet, Token Ring, or 10 Base T type local area network.
The Ethernet system is characterized by a coaxial cable which serves as a bus. The nodes of the system (e.g., terminals, printers and other devices) are connected to the cable and assigned a unique address.
A Token Ring LAN is a circular network similar to the Ethernet system with the exception that a token is used to control access to the network. The token is a packet of signals that is passed from node to node. The node that has the token has control of the network with respect to the transmission of data to other nodes. When the node has completed a transmission, the token is released for acquisition by another node.
The 10 Base T local area network is characterized by the use of a pair of twisted wires as a connector between nodes arranged in a star configuration around a controlling hub.
With each system, an interface is required between the network and the host. The interface typically includes a frontplane for connection to the network and a backplane for connection to the host. Conventional local area network interfaces typically include a microprocessor and a single internal bus. The microprocessor typically ties up the internal bus for instruction fetch and execution operations. This precludes the use of the bus for input and output (I/O) operations thereby slowing the operation of the system.
Some interfaces have been equipped with more powerful processors which tend to be less restrictive on I/O operations. However, these processors are expensive and typically require extensive, costly changes in the architecture of the interfacing system.
Accordingly, there is a need in the art for a fast and inexpensive system for interfacing a local area network to host.